Discussion of Phylogenetic Relationships

Only Rytidocystis polygordiae has been characterised using electron microscopy and phylogenetic analyses of small subunit (SSU) rDNA sequences (Leander & Ramey 2006). It is the first available sequence for this group of apicomplexans. The intracellular sporozoites posses a conoid, rhoptries, micronemes, dense granules, and a posteriorly positioned nucleus. The phylogeny indicates a close relationship between R. polygordiae with some environmental phylotypes of unknown morphological identity. The sequence branches at the unresolved base of Apicomplexa and contradicts the traditional placement within the coccidian group. The basal radiation of apicomplexa sufferes from (i) poor taxon sampling and (ii) inability of SSU rDNA to resolve this region.

Very little is known about the coral parasite Gemmocystis (Upton and Peters, 1986). The molecular identity of these presumably coccidian parasites remains puzzling. While there is not yet a true sequence of Gemmocystis, there are a few sequences that are apparently from a coral apicomplexan (Toller et al., 2001 & 2002). Whether these coral reports apply to Gemmocystis is not clear but deserve further scrutiny.

Toller, W. W., R. Rowan, and N. Knowlton. 2001. Zooxanthellae of the Montastraea annularis species complex: Patterns of distribution of four taxa of Symbiodinium on different reefs and across depths. Biological Bulletin 201:348-359.

Page: Tree of Life
Agamococcidiorida Levine 1979.
Authored by
Jan Šlapeta.
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